Well-dispersed nanosized clusters of metallic platinum were obtained by decomposition of ethylenediamine complexes immobilized on amorphous silica surfaces. Samples before reduction were obtained by potentiometric titration in a heterogeneous liquid/solid system in different pH ranges. The proposed easy and inexpensive method for characterization of metal-ligand interactions provides new information about phenomena taking place at the molecular level, depending on the type of support, type of agent coupling with the ligand, and type of metal. The systems obtained were characterized by TEM, XRPD and hydrogen chemisorption. The catalytic properties of the systems studied were tested in N₂O decomposition.